In orthodontics, tooth movement generally requires placing force on the tooth, such as with braces. These forces require an anchoring point, such as a neighboring tooth. However, since the anchoring tooth is exposed to the same magnitude of reactive forces as the tooth or teeth being treated, the anchoring tooth often moves to an undesirable position. While these movements can be ignored for minor cases, in other cases, they can interfere with the orthodontic treatment. In extreme cases, the movements can require orthogenetic surgery, which has a relatively high morbidity rate, to replace the anchoring tooth.
To solve these problems, temporary anchorage devices (TADs) have been developed. These TADs are temporary implants that are placed in the jaw bone and can be connected an orthodontic device on the target tooth by springs or elastics. TADs can allow the target tooth to move in the desired direction while minimizing the effect on adjacent teeth.
Currently, there are two different designs for TADs. The first design is in the form of a single screw that is placed without surgery directly through the gum to the bone. However, this form of TAD, because it is a single screw, can be unstable and result in movement or dislodging of the screw during the anchoring process. Further, this type of screw mechanism traditionally has a screw thread extending the entire length of the device, which can both create irritation in the gums and provide a space for bacteria and other microorganisms to enter and cause infection.
The second TAD design includes an implantable surgical plate with multiple screws holding the external plate in place. This design must be implanted by a surgeon underneath the soft tissue such that the plate lies directly against the bone and is held in place with the screws. The surgical plate advantageously provides stability to the TAD. This design, however, requires the patient to undergo surgery, significant increasing the cost and risk associated with the design. Further, once implanted, the TAD cannot be adjusted or removed without further surgery. Moreover, if the external plate or the screws become loose over time, significant irritation can occur as a result of having the loose device in a closed space underneath the gums.
Accordingly, a TAD design that solves these problems is desired.